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speedometer (spelling) on my 79 is swinging 60 to 70 mph at steady hiway speed what do i need to look at to fix this.
 

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Mine did that and the tack would jump from 0 to 7 repeatedly. Change the speedo cable. Not expensive. Also, check to see if the cable itself is not loose on the tranny. Mine was. That stopped it for a while tightening it up but it had been loose evidently for some time and roughed the end of the cable shaft to where it was not giving me an accurate reading. I ordered the tack cable and the speedo cable and it works fine now. Best of luck. It worked for me. :partyon: :thumbsup:
 

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One other thing. I remember the closeness of the two cable to the box. You will most probably have to remove the tack cable first and install the speedo cable first and then reinstall the tack cable. I believe in my recollection the tack cable is on top and the speedo is below it . It is a fine thread connector also, so do not try to jam nothing in there and be sure there are no kinks in the thing or it will be a trash install. I put the new cable on the tranny first I think and then the cable box. You can also reach behind the speedometer under the dash and see if the short cable is not loose. Mine was. It just snaps on and off the gauge. :thud: Sometimes I forget......;)
 

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Hey Cool80, did you have to drop your steering column in order to get good access behind your speedo? I'm trying to pull out my cluster over the steering wheel today to replace my cable, and it doesn't look like I can pull the plastic housing all the way out without dropping the column.
 

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I would reach up in the connection also behind where the speedometer is, it may have come loose or they guy you bought it for may have disconnected it like the guy I bought mine for. It is no big deal to put the cable in whatsoever. Not complicated at all. Like I said on that box where the cables are for the tach and the speedo are one on top the other with fine thread connectors. I tried to put it on without takin the tack cable off from underneath but no doing. When I got that off it came off easy. Speedo is the bottom one and the tach is the top one. And when you put the new one on go from the tranny and hook that end up and then hook it up to the box that runs the darn things. I have not yet put my tach cable on but neither were very expensive. Sure is nice to know how fast you are going though once you get them fixed. They are right there under the master cylinder. Because the fastners are so close together that is why it is so much easier to take the tack cable of first. Oh, it is plastic like clips than connect to the gauges. Vibration or just fatique could have made them fail also. And if that steering column gets a bit loose do not try and do that yourself. By the time you buy a wheel puller and all the parts to do the job you have wasted your money. Bring the damn thing to a mechanic that knows what he is doing. There are little bitty parts in that steering column and when I saw that in the manual I thought to myself. NOPE! You gone to the shop baby! :cheers:
 

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speedometer (spelling) on my 79 is swinging 60 to 70 mph at steady hiway speed what do i need to look at to fix this.
Hey, mine is doing something similar. Please let me (us) know if you follow the advice of the guys above and how it works out for you, what the fix is.

Good luck!
 

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If what I told you does not work then mabey they are right about the gear. Hope it is not the tranny gear. I looked at the new cable and the old cable. I got lucky I guess. It does not skip a beat. Do not know about this dropping the column gig. Take the frikin seat out where you have room to glance at it and you can see everything back there. There is not much room under there to start with. The dash is just where your gauges are plugged in. It has nothing to do with nothing unless it is disconnected or loose. It is in the cable. They get worn out like I said in my other threads. I first thought GREAT another big ticket item. It was not so I bought both of them. I am not gonna lie to no one. I am telling the truth here. I spent almost 500 bucks trying to find the reason my 79 would not start until I unplugged the damened Tach filter. All it is in all actuality is a supressor so the radio does not have static. I listen to 350 Am! the best small block channel I can find!
 

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Read my thread Adam. This guy who owns a group I belong to in Pa finally found the problem when it got to the tach filter. Others were telling me this crap and that crap. After like I said spending money for all that crap I was furious. I even called a frikkin mechanic and he told me it was the distributor. NO it was not. He was right but it was not the item he suggested. It was a simple matter of unpluggin the tach filter. The damn thing started right up. I even bought a brand new Optima battery thinkin that was the problem. NO DICE. I had no problem changin the speedometer cable either. Just one of the problems like brakes when you buy a C3. Just the way it is. :thud:
 

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Hey Cool80, did you have to drop your steering column in order to get good access behind your speedo? I'm trying to pull out my cluster over the steering wheel today to replace my cable, and it doesn't look like I can pull the plastic housing all the way out without dropping the column.
When I swapped the 85 MPH speedo for the 165 MPH unit, I just removed the clear plastic cover which allowed access to the speedometer and cable. I didn't have to do anything with the steering column.
 

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For the speedo cable DON'T drop the steering column.

Feel under the dash and find the cable going to the speedo. There's a flat tension clip that the cable goes through. On the bottom side of the clip is a tab. Push in on the tab of the clip and pull the cable out.

I went out last night and did mine with one hand just so I'd be sure before I posted this.

When you put it back in, just push the cable in and it will click itself in place.
 

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For the speedo cable DON'T drop the steering column.

Feel under the dash and find the cable going to the speedo. There's a flat tension clip that the cable goes through. On the bottom side of the clip is a tab. Push in on the tab of the clip and pull the cable out.

I went out last night and did mine with one hand just so I'd be sure before I posted this.

When you put it back in, just push the cable in and it will click itself in place.
So, you didn't even remove the gauge cluster? You could just reach up behind the dash to pull it out?
 

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So, you didn't even remove the gauge cluster? You could just reach up behind the dash to pull it out?
Yeah. I haven't had to do the Tach so that I'm not sure about. But the speedo comes right out, and goes right back in.
I changed mine from cruise to single line. There's a rubber grommet that's in the firewall and it comes right out too. It might be hard as a rock from age but mine came out and I reused it. Popped right back in.
 
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